The field of the invention relates to lithotrity and more particularly to the probes used for crushing urethral calculi.
Lithotrity (also commonly referred to as lithotripsy) is a well-known process for removing concretions, such as calculus stones, within human ducts such as the ureter or kidney. Under the process, a rigid probe is inserted into the body of the subject with a first end juxtaposed against the concretion. An ultrasonic signal is imposed onto the probe from a second end to break up the concretion.
The ultrasonic signal is typically generated by use of an electrically stimulated ultrasonic motor which may be rigidly attached to the probe. A variable power supply is used to supply a controlling signal to the ultrasonic motor.
The probe used is often hollow and typically made of an impervious material such as stainless steel. Often the tip used to contact and break up calculus stones is fabricated of a harder material.
The length of the probe is usually selected to be an integer multiple of one-half wavelength at the operating frequency. Selecting the probe to be an integer multiple of one-half wavelength at the operating frequency (and appropriate selection of tube thickness and coupling components) causes the probe to function as a resonator. The use of the probe as a resonator reduces the net power required to operate effectively.
An internal passageway of the probe is used to carry away debris generated by break-up of the concretion. The flow of fluid also functions to cool the probe during lithotripsy.
While lithotripsy using a rigid.probe.is effective, it is subject to a number of difficulties. As a concretion is broken-up, debris often accumulates and clogs the internal passageway of the probe. Clogging of the internal passageways of the probe often causes overheating of the probe, especially at higher power settings.
During break-up of the concretion, the probe will often bore a hole into the concretion and become lodged inside. Where relative movement between the probe and concretion ceases, break-up of the concretion effectively stops.
Accordingly, it is an object of the invention to restrict entry of debris into the passageway inside the probe until break-up of the concretion has progressed to a point where clogging is avoided.
It is a further object of the invention to provide a mechanism that prevents lodging of the probe tip within the concretion during break-up of the concretion.
Briefly, these and other objects are provided by a rigid catheter for use in lithotripsy. The catheter includes a rigid tube adapted to engage a lithotripsy power supply and a restriction in an internal diameter of the rigid tube proximate a power delivery end of the rigid tube.
The catheter may also include an enlargement on an external diameter of the tip. The tip may also be fabricated of a material considered to be very hard.